1. Field of the Invention
Aspects of the present invention generally relate to a receiving apparatus and method, and more particularly, to a receiving apparatus and method included in a multiple-input and multiple-output (MIMO) system of a mobile communication system, and a transmitting apparatus and method corresponding to the receiving apparatus and method.
2. Description of the Related Art
A multiple-input and multiple-output (MIMO) scheme is one technique for speeding up communication between wireless devices. The MIMO scheme is based on signal input/output operations using a plurality of antennas. The MIMO scheme is characterized in that a plurality of transmission data can be collectively transmitted at the same timing and at the same frequency using a plurality of different antennas. Thus, with an increase in the number of channels that can be transmitted at the same time, the amount of data that can be transmitted per unit time can also be increased by the increase in the number of channels. This scheme can improve communication speed without increasing occupied frequency band.
However, due to the simultaneous transmission of a plurality of modulation signals having carrier components of the same frequency, a reception side needs a way to separate the modulation signals. Thus, the reception side estimates a channel matrix indicating the transmission characteristics of a transmission path and separates a transmission signal corresponding to each sub-stream from a reception signal based on the estimated channel matrix. The channel matrix is estimated using a pilot symbol.
A transmission signal needs to be precisely reconstructed for each sub-stream by sufficiently removing influences of noise added to the transmission path or interference between sub-streams. Recently, various techniques for MIMO signal detection have been developed. Much attention has been given to a multi-user MIMO system including a plurality of communication devices capable of performing MIMO signal transmission. Signal detection in a multi-user MIMO system may use a minimum mean squared error (MMSE) detection method. The MMSE detection method involves processes in which a reception side calculates a signal power to interference plus noise power ratio (SINR) after MMSE detection in order to feed the calculated SINR back to a transmission side and the transmission side sets transmission control parameters based on the SINR in order to improve transmission characteristics. In order to further improve transmission characteristics compared to the MMSE detection method, the reception side in the multi-user MIMO system may use a maximum likelihood (ML) detection method.